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In this study, poultry manure compost and organic fertilizer were added to soils derived from basalt, granite, and river alluvial deposits for use as soil parent materials. Following incubation periods of 30 or 60 days at 25 °C, the physical and chemical properties and adsorption characteristics of the soils were studied. The results indicated that the application of poultry manure compost or organic fertilizer increased the available phosphorus (P) and organic matter content in all soils; however, the quantity of P and organic matter decreased with an increase in incubation time. The organic materials added via the treatments reduced the strength of P adsorption by the soil derived from basalt. For soils derived from granite and river alluvial deposits, the strength of P adsorption declined after poultry manure compost was added, but increased after the application of organic fertilizer. All soil treatments derived from basalt fitted well with the three adsorption isotherm equations. For soils derived from granite and alluvial deposit as parent materials, the data conformed to the three adsorption models in the order: Langmuir > Freundlich > Temkin. The maximum phosphate buffering capacity (MPBC) and standard P retention (SPR) of soil derived from basalt decreased following the application of poultry manure or organic fertilizer, whereas changes in MPBC and SPR for soils derived from granite and alluvial deposits were dependent on the organic content and incubation time.

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Iron is the first abundant transition metal in the Earth's crust; soils in subtropical and tropical zones contain a large amount of free Fe oxide and have thus been paid increasing attention. In this study, 22 soil samples were collected from the A (0-20-cm) horizon in South China and divided into three groups (i.e., vegetable soils in Pearl River Delta, orchard soils in Pearl River Delta, and forest soils in tropical zone). Two types of experiments, one without buffer 2-(/V-morpholino)ethanesulfonic acid (MES) and another with MES, were conducted to investigate the effect of pH and weathering indices on the reductive transformation of 2-nitrophenol (2-NP) on soils. Kinetic measurements showed an increase in pH resulted in an enhanced reaction rate (k) of 2-NP reduction. From cyclic voltammogram tests, the enhanced activity of Fe(ll) species was attributed to the negative shift of peak oxidation potential of the Fe(lll)-Fe(ll) couple. The results were subjected to statistical analysis, including the evaluation of variance and correlation, and the application of stepwise regression. Significant differences in k values were obtained in the different soil types and parent materials. The reaction pH proved to be an essential factor in 2-NP reductive transformation, and the weathering indices of soils had a critical effect on the 2-NP reductive transformation processes in soils. With an increase in the level of soil desilicification and allitization from Groups I to III, the k value increased consistently in the order of the decrease in the weathering indices. These findings improve our general understanding of the effect of pH and weathering indices on soil Fe redox chemistry and provide valuable information on the implications for research on soil pollution control.

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